Vacuum switch cam operating mechanism with contact loading compression spring

ABSTRACT

A single reciprocable cam bar simultaneously operates three vacuum interrupters. Cam follower motion is transmitted by precompressed contact loading springs to the movable contacts to assure high contact pressure, and the precompressed contact laoding springs exert substantially constant force regardless of the amount of contact erosion or overtravel. The cam bar is latched in switch closed position, and the forces of the three contact loading springs are additive to the force of the cam bar return springs to effect switch opening. Contact closing position is adjustable for each switch at a single point by varying deflection of the precompressed contact loading springs to thereby assure synchronized closing of the three interrupters. The motion of the contact operating rods is guided by pivoted yokes along a line substantially axial of the contacts to compensate for contact erosion.

United States Patent 91 Goodwin, Jr. et al. a g

[ Jan. 22, 1974 [75] Inventors: Edwin C. Goodwin, Jr., Canton;

Oscar L. Larkin, Saugus, both of Mass.; Heinrich H. Erni, Turgi,Switzerland [73] Assignee: Allis-Chalmers Corporation,

Milwaukee, Wis.

22 Filed! Aug. 4, 1972 211 App]. No.: 278,177

52 us. c1.... 200/153 LA, 200/144 B, 200/153 H, 335/131, 335/191 511 1pm 11011 33 42 HOlh 33/6 HOlh 3/42 [58] Field 61 Search... 200/144 B,'i5'3TA, 1531i, 153 G; 335/106, 27, 127, 131, 190, 191;

6/1971 Brunner 200/144 B X 4/1966 Lindsay 200/144 B X PrimaryExaminerI-Ierman J. Hohauser Assistant ExaminerRobert A. VanderhyeAttorney, Agent, or FirmRobert C. Jones; Robert B. Benson; Lee H. Kaiser[5 7] ABSTRACT A single reciprocable cam bar simultaneously operatesthree vacuum interrupters. Cam follower motion is transmitted byprecompressed contact loading springs to the movable contacts to assurehigh contact pressure, and the precompressed contact laoding springsexert substantially constant force regardless of the amount of contacterosion or overtravel. The cam bar is latched in switch closed position,and the forces of the three contact loading springs are additive to theforce of the cam bar return springs to effect switch opening. Contactclosing position is adjustable for each switch at a single point byvarying deflection of the precompressed contact loading springs tothereby assure synchronized closing of the three interrupters. Themotion of the contact operating rods is guided by pivoted yokes along aline substantially axial of the contacts to compensate for contacterosion.

20 Claims, 9 Drawing Figures PAIENTED 3.787.649

SHEET 2 (IF 5 PATENTEDJAHZZW I 3. 781', 649

' SHEET 5 OF 5 xii VACUUM SWITCH CAM OPERATING MECHANISM WITIICONTACTLOADING COMPRESSION SPRING This invention relates to an operatingmechanism for a plurality of vacuum interrupters.

DESCRIPTION OF THE PRIOR ART Operating mechanisms for a plurality ofvacuum interrupters are known, but push-rods which actuate the vacuuminterrupter contacts in certain prior art mechanisms are moved by athree-bar linkage which results in substantial lateral movement of thepush-rods and consequent erosion of the contacts. Such three-bar linkagerequired critical initial factory setting and subsequent fine fieldadjustment to maintain stability. Further, interphase coordination wasneither positively guided nor maintained throughout the operationsequence. Other prior art operating mechanisms for a plurality of vacuuminterrupters use separate cams for their push-rods'with the result thatit is difficult to syn chronize opening of and closing of the contactsfor the vacuum interrupters and more difficult to maintain theinterrupters in adjustment. Further, such prior art vacuum switchoperating mechanisms require adjustment at numerous points in theoperating mechanism of each interrupter in order to synchronize openingand closing of the plurality of interrupters. Certain prior artoperating mechanisms for a plurality of vacuum interrupters haveseparate contact opening means for each interrupter, and such openingmeans occasionally do not have sufficient force to separate theinterrupter contacts'if they freeze or become welded during use.Further, failure of one vacuum interrupter often caused dynamicunbalance of the three bar linkage operating mechanism of prior artvacuum switch actuating means and resulted in opening of all threeinterrupters.

OBJECTS OF THE INVENTION An object of the invention is to provide animproved actuator for a plurality of vacuum interrupters.

Another object of the invention is to provide a switch actuator havingmeans for latching a plurality of interrupters in closed position andstored energy means for simultaneously opening the plurality ofinterrupters.

Yet another object of the invention is to provide a switch actuatorhaving a single cam bar which effects simultaneous synchronizedoperation of the movable contacts of a plurality of electricalinterrupters.

A further object of the invention is to provide an operating mechanismfor a plurality of vacuum interrupters wherein all interrupter contactsare inherently synchronized and contact loading variation resulting fromcontact erosion is minimized.

A still further object is to provide an operating mechanism for aplurality of vacuum interrupters having means to correct each phase fordeviations caused by manufacturing tolerances or by wear.

Still another object of this invention is to provide an actuator for aplurality of vacuum interrupters having a single support plate on whichthe operating mechanism and the tripping mechanism for the plurality ofinterrupters is mounted.

A further object of the invention is to provide an actuator for aplurality of vacuum interrupters which applies substantially axialclosing forces simultaneously to the movable contacts of theinterrupters.

and precompressed contact loading springs which exert vsubstantially-constant force and transmit closing motion to the movablecontacts to thus prevent damage to the vacuum interrupters.

Still another object of the invention is to provide an improved actuatorfor a plurality of vacuum interrupters having precompressed contactloading spring means for holding the interrupter contacts closed with asubstantially constant .force so that contact pressure remains uniformirrespective of erosion of the contacts.

Still another object of the invention is to provide an operatingmechanism for a plurality of vacuum interrupters having precompressedcontact loading spring means in each of the interrupters for effectinghigh pressure contact engagement and'wherein the forces of such contactloading spring means of all of the interrupters are additive to theforce of the switch opening springs to break open the contacts of anyone interrupter if they become welded during operation.

Yet another object of the invention is to provide an operating mechanismfor a plurality of vacuum interrupters wherein the failure of oneinterrupter cannot cause dynamic imbalance of the operating mechanismwhich in prior art apparatus often resulted in opening of allinterrupters when one vacuum interrupter failed.

A still further object of the invention is to provide an improvedoperating mechanism for three phase vacuum switches wherein contactclosing for each interrupter is easily adjusted at a single point toaccomplish synchronized closing of the three interrupters.

These and other objects and advantages of the invention will be morereadily apparent from the following detailed description when consideredin connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in front elevation of athree phase vacuum switch embodying the invention with parts broken awayto show internal construction of a vacuum switch and of the switchoperating mechanism;

FIG. 2 is a view in elevation, partly in vertical section, of the switchoperating mechanism shown in FIG. 1;

FIG. 3 is a horizontal section view of the actuator taken along lineIII-Ill on FIG. 2;

FIG. 4 is a view similar to FIG. 2 showing the position of the variousactuator components after the actuator has operated to close thecontacts of the interrupters;

FIG. 5 is an enlarged fragmentary view in vertical section taken alongline V-V of FIG. 2;

FIG. 6 is an enlarged fragmentary view in transverse vertical sectiontaken through a hanger assembly which secures the mounting plate to thesupporting base;

FIG. 7 is a schematic illustration of how substantially linear actuationof an interrupter movable contact is accomplished by the cooperativemovement of a pivoted yoke and the push-rod in a contact closing (oropening) movement;

FIG. 8 is an enlarged fragmentary view partly in horizontal section andpartly in plan of the latch mechanism taken along line VIII-VIII in FIG.4; and

FIG. 9 is an enlarged fragmentary view of the end of the latch mechanismlever in latching engagement.

DESCRIPTION OF THE INVENTION FIG. 1 of the drawing shows a three phasevacuum switch 20 comprising three vacuum interrupters 21, 21a and 21bwhich are operated simultaneously by a switch actuator 24. The vacuuminterrupters 21, 21a and 21b are identical and are bolted in an uprightposition on a supporting base 25 comprising the web of a horizontalstructural channel member 26, which, in turn, is adapted to be mountedon a suitable supporting structure 27 shown in FIG. 2. The actuator 24is likewise supported by the base 25 and is secured in dependingrelationship to the underside of the channel member 26 by means ofhanger assemblies 81 and 82 which are secured to the channel member 26by bolts.

The vacuum interrupters 21, 21a and 21b are similar and the descriptionof the switch 21 will likewise apply to interrupters 21a and 21b, andcorresponding parts will be identified with the same reference numberwith an addition of a letter suffix to identify the particularinterrupters and associated mechanism. The interrupter 21 includes apair of ceramic hollow upper and lower insulators 28 and 29 disposed inaxial alignment. The lower insulator 29 is mounted in a lower metallichollow cup member 31 which is bolted to the top surface of channel 26.The upper end of the insulator 29 receives a cup member 32 similar tothe cup member 31. A similar arrangement is provided for the upperinsulator 28 wherein there are provided lower and upper hollow metalliccup members 33 and 34. A metallic terminal 36 having a clearance openingtherethrough for the interrupter operating rod is interposed between thecup members 32 and 33. The upper and lower insulator members 28 and 29are rigidly secured together by means of bolts 37 which extend throughsuitable aligned openings provided in terminal 36 and in the radialflanges of cup members 32 and 33. A metallic cap terminal 38 is boltedor otherwise secured to the upper cup member 34 and serves as a supportfor a depending stationary contact rod 39 of the vacuum interrupter. Thecup members 31 and 32 associated with the lower insulator 29 are bondedthereto. by suitable bonding material such as Portland cement, epoxyresin or the like. In like manner, the cup members 33 and 34 associatedwith the upper insulator 28 are likewise bonded thereto by the same typeof bonding material.

The stationary contact rod 39 extends downwardly into a glass vacuuminterrupter 41 that is supported in the hollow upper insulator 28.Vacuum interrupter 41 has a circumferential flange at its lower endwhich is fastened by screws (not shown) to the metallic terminal 36. Amovable contact rod 42 extends through the bottom end of vacuuminterrupter 41 and through the opening in terminal 36 in axial alignmentwith the stationary contact rod 39 and is movable into engagement withstationary contact 39. The movable contact 42 is shown in the openposition and is movable axially into abutting engagement with thestationary contact 39 to complete an electrical circuit through theinterrupter between terminals 36 and 38. The ends of vacuum interrupter41 through which the contacts 39 and 42 extend are sealed in a wellknown manner.

An electrical connection is established between movable contact 42 andthe terminal 36 by a plurality of electrically conductive flexibleshunts 35. The shunts 35 are secured to the under surface of theterminal 36 and to the surface of a hollow metallic connector 40 whichreceives the end of movable rod contact 42.

The contact 42 is moved axially by an actuating rod or push-rod 43 ofinsulating material that extends up wardly through the insulator 29. Theactuating rod 43 at its upper end is provided with the metallicconnector 40 which receives the lower end of the movable contact rod 42.The lower end of the push-rod 43 is secured to parallel coupling members44. As shown in FIG. 5, the lower end of the coupling members 44 arebifurcated so as to provide spaced parallel legs 46 and 47 which extenddownwardly between a pair of horizontally extending arm portions 48, 49of a pivoted U-shaped bracket yoke 51 which guides the movement ofpushrod 43 in a straight line axial of movable contact rod 42. As shownin FIGS. 2, 3 and 5, bracket yoke 51 has spaced arms 48 and 49 extendinghorizontally to the left disposed on opposite sides of legs 46 and 47and a pair of spaced arms 103 and 104 extending horizontally to theright. The arms 48 and 49 are disposed between the upstanding legs 52and 53 of U-shaped stirrup 54.

The leftwardly extending arms 48 and 49 of the pivoted U-shaped yoke 51are disposed to bracket a horizontally reciprocable cam bar 55, FIG. 5,which effects simultaneous axial movement of the movable rod contacts42, 42a and 42b of the three interrupters 21, 21a and 21b. A bolt 56passes through suitably aligned openings in the legs 52 and 53 of theU-shaped stirrup 54, through the arms 48 and49 of the bracket yoke 51,and through the leg members 46 and 47 of the coupling members 44, asshown in FIG. 5. Rotatably mounted on bolt 56 is a cam follower roller57 which is engaged in a cam slot 58 in the left end of the cam bar 55,as shown in FIGS. 2, 4 and 5.

As viewed in FIG. 5, the spaced dependent legs 46 and 47 of the couplingmembers 44 receive the head 61 of a bolt 62 that extends downwardlythrough a suitable opening in the horizontal cross bar of the U-shapedstirrup 54. The head 61 of bolt 62 is secured to the depending ends ofthe legs 46 and 47 by a pair of bolts 63, one of which is shown in FIG.5, passing through clearance holes in head 61. Bolt 62 provides apositive connection between stirrup 54 and coupling members 44 duringcontact opening while permitting relative movement therebetween duringcontact closing so that the interrupter contacts can be held closedunder high pressure by precompressed contact loading springs 66 and 67.

For the purpose of maintaining high pressure contact of the movablecontact 42 with stationary contact 39 irrespective of the amount ofovertravel of cam follower roller 57, a pair of concentric nestedprecompressed contact loading springs 66 and 67 are cooperativelyarranged to transmit contact follower motion to the contact operatingrod 43 and thus apply the required contact pressure to the movablecontact 42 when it is in engagement with stationary contact 39. As shownin FIG. 5, the springs 66 and 67 are of the compression type and arearranged in concentric nested relationship about the bolt 62. The innerspring 66 surrounds the bolt 62 so that its upper end engages the lowersurface of the bolt head 61 and its lower end is in engagement with thecross bar of the U-shaped stirrup 54. The outer spring 67 is of the samecompressed length as, but has a larger internal diameter than innerspring 66 and at its upper end engages the head 61 and at its lower endengages the cross bar of the U-shaped stirrup 54.

The lower depending end of the bolt 62 passes through a clearance holein the cross bar of stirrup 54 and is threaded at 68 and receives a pairof interengaging nuts 69 and 71 which are self-locked on the bolt 62.Bolt 62 pre-compresses contact loading springs 66 and 67 to apredetermined deflection so that they exert a force which issubstantially constant regardless of further deflection. When stirrup 54is moved upwardly by cam follower roller 57, springs 66 and 67 urgecoupling member 44 and push-rod 43 upwardly to actuate movable contactrod 42 into engagement with stationary contact 39 with the substantiallyconstant force of precompressed springs 66 and 67. This contact forceremains substantially uniform regardless of limited overtravel ofstirrup 54, and bolt 62 provides a positive connection between stirrup54 and coupling members 44 during contact opening.

The operating means for movable contact 42 of interrupter 21 thusincludes cam slot 58 in cam bar 55, cam follower roller 57, bolt 56which couples cam follower S7 to stirrup 54, contact loading springs 66and 67 which transmit contact closing motion from stirrup 54 to couplingmembers 44 and bolt 62 which preloads springs 66 and 67 and transmitscontact opening motion to coupling members 44, contact operating rod 43and movable contact rod 42, and bracket yoke 51 which at one end pivotsabout pin 98 and operatively engages bolt 56 at its other end to guidecoupling members 44 is essentially straight linemotion as it is actuatedby cam follower roller 57.

The cam bar 55 is reciprocable horizontally to effect the simultaneousupward movement of the push-rods 43, 43a and 43b to actuate the movablecontacts 42, 42a and 42b axially. As shown in FIGS. 2, 3'and 6, the cambar 55 is slidably supported by supporting strap assemblies 81 and 82which are mounted in spaced relationship from the underside of thechannel member 26. As shown in FIG. 6, the strap assembly 81 includes apair of spaced L-shaped members 81a and 81b which are secured by bolts88 and 89 to lugs 86 and 87 depending from channel member 26. The strapassembly 82 is similarly arranged and provided with a pair of L- shapedmembers 82a and 82b which are likewise secured in spaced relationship bymeans of bolts 93 and 94 to lugs 91 and 92 depending from the channel26. The cam bar SSis movably supported for reciprocation between theL-shaped members 81a and 81b of the assembly 81 and between L-shapedmembers 82a and 82b of assembly 82 by rollers 96 and 97 respectivelywhich are rotatably supported on associated bolts 98 and 99. The rollers96 and 97 are disposed in elongated horizontal guide slots 101' and 102in the cam bar 55. The bolt 98 protrudes through clearance apertures inthe spaced apart depending legs of L-shaped members 81a and 81b, and thebolt 98 also serves to support the rightwardly extending portions 103and 104 of the U- shaped bracket yoke 51 so that yoke 51 pivots on bolt98. A similar arrangement is provided for the bracket yoke 51b which hasits leftwardly extending arms 106 and 107 connected by the bolt 99 onwhich the roller 97 is supported so that bracket yoke 51b pivots on bolt99.

A component mounting plate 111 is supported in a vertical plane belowcam bar in depending relationship from the strap assemblies 81 and 82.As shown in FIG. 6 the plate 111 is disposed between and welded to theleg members 81a and 81b of the assembly 81 and also to the legs 82a and82b of the assembly 82.

As shown in FIGS. 2 and 3, the bracket yoke 51a associated with thecoupling member 44a has its leftwardly extending arms 48a and 49asupported by a bolt 98a that extends through aligned openings providedin the arms 48a and 49a. The bolt 98a is also provided with a rollermember 119 similar to the rollers 96 and 97. The roller 119 is disposedwithin an elongated horizontal guide slot 121 in cam bar 55. The bolt98a is disposed in upright strap members 122 and 123 that are welded oneither side of the component mounting plate 111. Thus the cam bar 55 ismovable in a horizontal plane, being guideably supported for movement bymeans of the rollers 96, 97 and 119 which operate in the guide slots101, 102 and 121 respectively. As viewed in FIG. 2, the leftwardmovement of the cam bar 55 will move push-rods 43, 43a and 43b upwardlyfor actuating the associated movable contacts 42, 42a and 42b associatedwith the interrupters 21, 21a and 21b. The vertical upward movement ofthe push-rods 43, 43a and 43b upon leftward movement of the cam bar 55is accomplished by cam slots 58, 58a and 58b in the cam bar 55. The camslots 58, 58a and 58b are identical and the description for the cam slot58 will apply to the cam slots 58a and 58b. As shown in FIG. 4, cam slot58 has a lower horizontal cam track portion 126 and an upper horizontalcam track portion 127 which are connected by an upwardly inclined camtrack portion 128. With the cam bar 55 located in its extreme positionto the right, as depicted in FIG. 2, cam follower roller 57 associatedwith the push-rod coupling member 44 is located in the lower cam trackportion 126 wherein the movable contact 42 is in open position, as shownin FIG. 1. As the cam bar 55 is moved to the left, the cam followerroller 57 tracking in the cam slot 58 is cammed upwardly following theupwardly inclined cam track portion 128 to the upper cam track portion127. As the cam follower roller 57 tracks in the cam slot 48, stirrup54, coupling members 44 and the push-rod 43 are moved axially upward,thereby moving the contact 42 into an abutting engagement with thestationary contact 39. The cam follower roller 57 is rotatably supportedon the bolt 56 which passes through aligned openings in the upwardlyextending legs 52 and 53 of the stirrup member 54, through theleftwardly extending arms 48 and 49 of the bracket yoke 51, and throughvertically elongated openings 131 and 132 (See FIG. 5) in the dependingleg portions 46 and 47 respectively of the coupling members 44.- Thus,as the cam roller 57 tracks in the cam slot 58, the bolt 56 will movewith the roller 57 and, in turn, will force leftwardly extending ends 48and 49 of the bracket yoke 51 to pivot upwardly about the bolt 98. Thebracket yoke 51 thereby causes bolt 56 to move in an arcuate path havingbolt 98 as the center and thus operates to maintain the push-rod 43 in avertical position so that it moves substantially in a straight line andthe movable contact 42 engages in face-to-face abutting relationshipwith the stationary contact 39. As the bolt 56 moves upwardly with thecam follower roller 57, it moves within the vertical openings 131 and132 in the depending ends 46 and 47 of the coupling member 44 whichmovement of stirrup 54 is transmitted to coupling members 44 by springs66 and 67.

This pivotal connection between the bracket yoke 51 and the lower end ofthe coupling members 44 limits lateral movement of the lower end of thepush-rod 43 so that it moves in a substantially straight line of movablecontact 42.

This movement is best illustrated in FIG. 7 wherein the identifyingreference numbers associated with the related mechanical components areutilized for the schematic showing of the parts. Thus, in FIG. 7 thepoint 56 represents the bolt 56 which is coaxial with cam followerroller 57 tracking in the cam slot 58. The arcuate line 131 representsthe path followed by the bolt 56 as the cam follower roller 57 operatesto close the contact 42. Point 98 in FIG. 7 represents the axis of bolt98 about which the bracket yoke 51 pivots as the cam bar 55 moves to theleft for closing the contacts 42. The lower horizontal line in FIG. 7represents the lower cam track portion 126, the middle horizontal linerepresents the midpoint in the connecting inclined cam track portion128, and the top horizontal line represents the upper cam track portion127 wherein the full force of the contact loading springs 66 and 67 isexerted to maintain contact 42 in high pressure engagement withstationary contact 39. Thus, with the cam bar 55 in its full rightwardposition, depicted in FIG. 2, the contact 42 is in open position. Inthis position, the roller 57 is in the lower cam track portion 126. Asthe cam bar 55 is moved leftwardly, the roller 57 following the cam slot58 moves out of the lower cam track portion 126 and up the inclined camtrack portion 128. As the cam bar 55 moves leftwardly to effect closingof the contacts, the lower end of the pushrod 43, represented by thepoint 56 in FIG. 7, will move in an arcuate path represented by the line131. Inasmuch as the vertical stroke of push-rod 43 is very smallcompared to the distance between bolt 56 and pivot point 98, it will beappreciated that bolt 56 can only move a very slight distance in thehorizontal direction and that bracket yoke 51 guides push-rod 43 in anessentially straight line, or axial direction during opening and closingof the contacts. When roller 57 moves upwardly out of the inclined camtrack portion 128 into the upper cam track portion 127 represented bythe top horizontal line 127 in FIG. 7, the axis of the push-rod 43 andmovable contact rod 42 are in the vertical plane represented by the line130, thereby. insuring face-toface abutting engagement of the contacts42 and 39. The bracket yokes 51a and 51b associated with pushrods 43aand 43b operate in the same manner as bracket yoke 51. Alllof themovable contacts 42, 42a and 42b engage their associated stationarycontacts 39, 39a and 39b simultaneously when the cam follower rollers57, 57a and 57b are at the midpoint of their inclined cam track portions128, 128a and 128!) respectively. As the cam follower rollers 57, 57aand 57b move beyond the midpoints of their associated inclined cam trackportions 128, 128a and 128b respectively. As the cam follower rollers57, 57a and 57b move beyond the midpoints of their associated inclinedcam track portions 128, 128a and 128b respectively, the preloadedcontact loading springs 66-67, 66a-67a, and 66b-67b urge the movablecontacts 42, 42a and 42b into high pressure engagement with thestationary contacts 39, 39a and 39b respectively, and such contactpressure remains substantially constant during any overtravel of thestirrups 54, 54a, 54b as the cam follower rollers are cammed further upinclined cam track portions I28, 128a and l28b as described hereinafter,thereby preventing bounce and consequent erosion of the movable contacts42, 42a and 42b.

Known operating mechanisms for three phase vac uum switches use athree-bar linkage which causes considerable lateral movement of thepush-rod and results in contact erosion and contact bounce. It will benoted that push-rods 43, 43a and 43b are free-floating and are guided bybracket yokes 51, 51a and 5 lb and from the cam follower rollers 57, 57aand 57b so that they move free of slide cam bar 55. Further, the centerof cam slots 58, 58a and 58b is at the same horizontal level as theguide slots 10l, 102 and I2] and is at the point of contact engagement.In this manner longitudinal movement of the push-rods 43, 43a and 43b ispositively controlled so that contact bounce is eliminated and lateralmovement of the push-rods is limited so that contact erosion isminimized.

In accordance with the invention the contact loading springs 66-67,66a-67a, and 66b-67b are loaded to a predetermined substantiallyconstant force so that high contact pressure is maintained even thoughthe contacts erode.

For affecting simultaneous closing of the three switches, the nuts 69,69a and 69b are adjusted on the end of the threaded portions of thebolts 62, 62a and 62b respectively. To this end, the cam bar 55 is movedleftwardly from the open switch position in which it is shown in FIG. 2to a half stroke position wherein the cam follower rollers 57, 57a and57b are midway up the inclined cam track portions 128, 128a and l28brespectively At this point a pin (not shown) is inserted through anopening 136, FIG. 1, in the L-shaped leg member 82a of the hangerassembly 82 when it registers with an opening (not shown) in the cam bar55 to lock the cam bar 55 in said half-stroke position. The nut 69 isthen turned relative to bolt 62 to move coupling members 44 upwardly ordownwardly until movable contact 42 just engages stationary contact 39.In a similar manner, the nuts 69a and 69b associated with the push-rods43a and 43b are adjusted so that movable contacts 42a and 42b justengage the stationary contacts 39a and 39b at the half-stroke positionso that contact closing is synchronized in all three phases. When thedesired adjustment has been efected, the pin (not shown) is removed fromthe aperture 136 to release the cam bar 55. Known operating mechanismsfor three phase vacuum switches require adjustment at a plurality ofpoints in each switch to synchronize closing of the three interrupters,and it will be appreciated that the disclosed structure requiresadjustment at only one point on each interrupter actuator to synchronizecontact closing in all three phases.

The contact pressure remains substantially constant irrespective of theamount of overtravel or of contact erosion. In the preferred embodimentthe contact pressure is approximately 88 pounds and varies only plus orminus four pounds from initial contact engagement until the end of thecam stroke. If the contacts of one interrupter freeze (weld) due toarcing, the predetermined force of the precompressed springs 66-67,66a-67a and 66b-67b of all three phases are additive to separate thecontacts.

In order to close the vacuum switches 21, 21a and 21b, an actuatingmechanism 141 is provided to move cam bar 55 to the left. Actuatingmechanism 141 may be electrically or manually operated as desired. Asshown in FIGS. 2 and 3, the actuating mechanism 141 includes a pair ofgenerally triangularly shaped bell crank levers 142 and 143 which arepivotally connected to the cam bar 55 on opposite sides thereof by a pin146, as shown in FIG. 3. The bell crank levers 142 and 143 are fulcrumedon opposite sides of mounting plate 111 by a pin 144 extending throughplate 111.

Pivotal movement of the bell crank levers 142 and 143 about the fulcrumpin 144 in a counterclockwise direction, as viewed in FIG. 2, willeffect the leftward movement of the cam bar 55 and closing orinterrupters 21, 21a and 21b. The bell crank levers 142 and 143 arelatched in their counterclockwise position to maintain the interrupters21, 21a and 21b closed. For latching the bell crank levers 142 and 143,as depicted in FIG. 4, a latch mechanism 150 engages a latch pin 55 thatextends through one leg of both of the bell crank levers 142 and 143.The latch mechanism 150 includes a latch trip lever 151 having dependingbifurcated legs 152 and 153 and which is pivotally supported on a pin154 extending through legs 152 and 153 and through a protrusion 156 ofthe mounting plate 111 at a cutout portion 160 of the mounting plate.Latch trip lever 151 is pivotally supported by the pin 154 with thebifurcated depending legs 152 and 153 disposed on opposite sides of themounting plate 111 and is biased in a counterclockwise direction. Thelatch trip lever 151 also includes an upstanding thumb portion 157 whichis operative to engage under the latch pin 155 that extends through thebell crank levers 142 and 143 at cutout portion 160. When theinterrupters are open and the bell crank levers 142 and 143- are intheir unlatched clockwise position, the latch pin 155 is disposedadjacent the side of the thumb portion 157 in the dotted line positionshown in FIG. 9. As the bell crank levers 142 and 143 are pivoted in acounterclockwise direction to the latched position wherein the switchcontacts are held closed, the latch pin 155 rides up and over aninclined surface 158, FIG. 9, of the thumb portion 157 to the solid lineposition shown in FIG. 9 wherein it rests on an arcuate surface 159 onthumb portion 157. With the bell crank levers 142 and 143 in fullcounterclockwise pivoted position, the upper arcuate surface 159 of thethumb portion 157 will move under the latch pin 155 to latch the bellcrank levers 142 and 143. As best shown in FIG. 8, the depending leg 153of the latch trip lever 151 is provided with a laterally extendingfinger 161. A tension spring 162 is secured at one end to the finger 161and at'its opposite end to a bolt 163 which is threadedly engaged in themounting plate 111 and extends outwardly therefrom; Thus the latch triplever 151 is biased by spring 162 so that the thumb portion 157 is movedin a counterclockwise direction to bring arcuate surface 159 under pin155 upon counterclockwise pivotal movement of the bell crank levers 142and 143.

A stop screw 164 threadedly engaged in the outer end of the finger 161is arranged to abut a stop 166 affixed to mounting plate 111 to limitthecounterclockwise movement of the thumb portion 157 at the solid lineposition shown in FIG. 9. In this latched position of bell crank levers142 and 143, a radius drawn from pin 154 as a center through the latchpin 155 will pass through the arcuate surface 159 slightly to the rightof the junction of the inclined surface 158 and the arcuate surface 159.In a preferred embodiment the adjustment is such that when the thumbportion 157 is in engage ment with the latch pin 155, the pin engagesarcuate surface 159 at a distance A shown in FIG. 9 no greater than oneeighth of an inch from the junction of the inclined surface 158 with thearcuate surface 159. This arrangement has been found most advantageousin effecting instantaneous tripping since the only force required isthat needed to overcome the coefficient of rolling friction, and a tripsolenoid 201 is only required to impart a slight clockwise rotation toleg 152 of the latch trip lever 151 to release bell crank levers 142 and143 and thus permit return of the cam bar 55 to the right to open theswitches.

Clockwise pivotal movement of the bell crank levers 142 and 143 fromtheir latch position, as depicted in FIG. 4, to their unlatchedposition, depicted in FIG. 2, to open the interrupters is effectedprincipally by a pair of interrupters opening springs 172 and 173disposed on opposite sides of mounting plate 111 and afixed at one endto a pin 174 extending through mounting plate 111 and at their oppositeend to a pin 175 extending through both bell crank levers 142 andaffixed above mounting plate 111. As the bell crank levers 142 and 143are pivoted in a counterclockwise direction to close the interrupters,interrupter opening springs 172 and 173 are placed in tension so thatthe energy stored therein will effect clockwise pivotal movement of thebell crank levers 142 and 143 to open the interrupters upon tripping ofthe latch mechanism 150.

Power actuation of the bell crank levers 142 and 143 in acounterclockwise direction to close the interrupters 21, 21a and 21b isaccomplished by a switch closing solenoid secured to a horizontallyextending plate 181 that is welded to a lower surface of mounting plate111 adjacent the left end thereof. The solenoid 189 is provided with aplunger 182 that is axially reciprocable within a cutout port on inmounting plate 111 when the solenoid 180 is energized. The plunger 182is connected to the lower left leg of the bell crank levers 142 and 143by links 183 and 184. The links 183 and 184 are pivotally connected attheir upper ends to the bell crank levers 142 and 143 by a pin 186, andthe lower ends of the links 183 and 184 bracket the plunger 182 and areconnected thereto by a pin 187 that extends through the plunger 182.Switch closing solenoid 180 may be energized from a battery (not shown)in an electrical circuit completed by a remote manual switch (not shown)or suitable automatic relaying means, and energization of the solenoid180 attracts the plunger 182 downwardly so that the bell crank levers142 and 143 are pivoted about the fulcrum pin 144 in a counterclockwisedirection, thereby moving the cam bar 55 to the left and closing theswitches. Closing solenoid 180 is selected to have a sufficiently highattractive force for plunger 182 to impart high dynamic speed to theoperating mechanism so that switches 21, 21a and 21b close within a halfcycle to prevent restrikes and high frequency transients but whichattractive force is not high enough to cause contact bounce.

As shown in FIGS. 2, 3 and 4, a manual switch actuating lever 191rotatable in opposite directions for closing and for tripping theswitches is secured to a shaft 192 that is rotatably supported in themounting plate 111. As viewed in FIGS. 2 and 3, upwardly inclined camoperating arm 193 disposed adjacent to the cam bar 55 is secured toshaft 192 for rotation therewith. The upper end of the arm 193 isprovided with an elongated slot 194 which receives a pin 196 secured inthe cam bar 55 as shown in FIGS. 2 and 3. Counterclockwise rotation ofswitch actuating lever 191 will rotate shaft 192 and pivot arm 193 in acounterclockwise direction to move cam bar 55 to the left through theconnection established between slot 194 and pin 196. As the arm 193pivots counterclockwise, it will force the cam bar 55 to moveleftwardly, FIG. 2, without imparting an upward force to the cam barwhich would tend to displace it from the horizontal because of theelongated slot 194 which permits free movement of the pin 196 upwardlyof the cam bar.

The manual switch actuating lever 191 is also operable in the clockwisedirection to trip the latch mechanism 150 and permit the cam bar 55 toreturn to the right and thus open the vacuum switches. To this end, atrip solenoid plunger actuating arm 195 is connected to the shaft 192for rotation therewith. The lower end of the arm 195 is urged by aspring 197 into engagement with the outer end of an actuating rod 198(See FIG. 2) which is supported in a bracket 199 that is attached totrip solenoid 201 so that rod 198 is aligned with plunger 204 of tripsolenoid 201. The trip solenoid 201 may be mounted by bolts (FIG. 8) tothe front face of mounting plate 1 11 so that trip solenoid plunger 204is adjacent trip lever 151. The rod 198 is maintained in its outwardposition by means of a spring 202 surrounding rod 198 and which at oneend abuts against the bracket199 and at its opposite end abuts against awasher 203, FIG. 2, which bears against a pin extending transverselythrough the rod 198. Movement of the rod 198 to the left, as seen inFIG. 2, will engage the rod 198 with the end of plunger 204 of tripsolenoid 201, thereby causing the plunger 204 to move axially to theleft, as viewed in FIG. 2. When solenoid plunger 204 moves to the leftit engages a horizontally extending finger 206 (See FIG. 8) that isintegral with leg 152 of the bifurcated latch lever 151. With the latchmechanism 150 in the switch open position depicted in FIG. 2, thespacing between the horizontally extending finger 206 of the latch leverleg 152 and the trip solenoid plunger 204 is sufficient to allow thespring biased thumb portion 157 of the latch lever 151 to pivot in acounterclockwise direction under the roller 155 to latch the operatingmechanism. With the cam bar 55 in its leftward position shown in FIG. 4wherein the contacts of the interrupters are closed, the thumb portion157 will be biased in a counterclockwise direction by the spring 162 sothat the arcuate surface 159 of the thumb member 157 engages under thelatch pin 155. With this condition obtained, the horizontally extendingfinger portion 206 will be in engagement with the outer end of thesolenoid plunger 204. As described hereinbefore, only a small force isrequired to pivot latch lever 151 and trip the operating mechanism, andspring 202 exerts a counter force against arm 195 and preventsinadvertent tripping of the switch such as might otherwise be caused bythe weight of a hotstick engaged in the eye at the end of the switchactuating lever 191.

Tripping of the switch operating mechanism may be accomplishedautomatically through energization of the trip solenoid 201, therebymoving solenoid plunger 204 to the left to pivot the latch lever 151 ina clockwise direction about the pin 156 and moving the thumb portion 157out of engagement with the latch pin 155. This releases the bell cranklevers 142 and 143 so that they pivot in a clockwise direction about thefulcrum pin 144 under the influence of the stored energy in the switchopening springs 172 and 173 aided by the additive force of contactloading springs 6667, 66a-67a and 66b-67b. This will effect a rightwardmovement of the cam bar 55, thereby disengaging the movable contacts 42,42a and 42b of the switches 21, 21a and 21b from the stationary contacts39, 39a and 39b.

To manually trip the switch operating mechanism, the switch actuatinghandle 191 is pivoted downwardly in a clockwise direction from theposition shown in FIG. 4, thereby rotating the shaft 192 and lever 195so that it pushes the rod 198 and solenoid plunger 204 leftwardly.Leftward movement of the solenoid plunger 294 will engage it with theextending finger 206 of the leg 152 of the latch lever 151, therebypivoting the latch lever 151 in a clockwise direction to release thebell crank levers 142 and 143. The stored energy in the springs 172 and173 then pivot the bell crank levers 142 and 143 about the fulcrum pin144 in a clockwise direction, thereby forcing the cam bar 55 to moverightwardly to open the switches.

As can be seen in FIG. 1, the switch actuating mechanism 24 is protectedboth from the weather and damage by a cabinet enclosure 208 which is inthe form of an envelope having an open upper end which engages the undersurface of the channel member 26. The cabinet enclosure 208 is held inposition by bolts 209 engaged within internally threaded lugs 210 thatare welded or otherwise secured to the lower surface of the mountingplate 1 11.

From the foregoing description, it can be readily seen that a rugged andsimplified arrangement has been provided in which a single cam bar 55effects the simultaneous opening or closing of a plurality of vacuuminterrupters. It will also be apparent that the single mounting plate111 for supporting the operating mechanisms for the three phase vacuumswitch results in a superior and simplified structure that is economicalto produce yet rugged in construction.

With the arrangement described, it will be apparent that if the contactsof one of the vacuum switches should freeze or weld, the additive forcesof all the nested contact loading springs 66 and 67, 66a and 67a and 66band 67b associated with the push-rods 43, a and 43b cooperate with thestored energy switch opening springs 172 and 173 to break the weldedcontacts apart. v

It is also apparent that the cam slots 58, 58a and 58b being formed inthe manner depicted with the upper track portions parallel to thedirection of cam bar reciprocation prevent overtravel of the movablecontacts 21, 21a and 21b, thereby preventing damage to the vacuuminterrupter bottles.

It should be understood that we do not intend to be limited to thesingle embodiment shown and described for many modifications andvariations thereof will be obvious to those skilled in the art.

We claim:

1. In an electric circuit breaker having at least three interrupters inparallel vertical array, said interrupters each having a pair ofseparable contacts one of which is stationary and the other of which isaxially movable into and out of engagement with said stationary contact;

operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts;

an elongated cam bar supported for reciprocal movement in a directiontransverse to the direction in which said movable contacts are movable;

a plurality of identical cam slots formed in said cam bar, one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam track portioninclined at an oblique angle to the direction of cam bar reciprocation,each cam slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving 'a camfollower;

a pivoted yoke for each cam follower and operatively connected to eachcam follower for guiding the lower end of said contact in such a mannerthat in the closing movement said movable contacts move in an arcuatepath of travel that terminates on a line that includes the axes of thecontacts when said contacts are in closed position to thereby provide awiping engagement between the contact faces of said contacts; and,

a contact loading compression spring for each of said contacts, saidloading compression spring being supported in position to provide forpredetermined high pressure engagement between the movable contact andan associated stationary contact irrespective of the amount of overtravel of an associated cam follower,

whereby movement of said cam bar in one direction will effectsimultaneous movement of all of said movable contacts in the samedirection into engagement with their associated stationary. contacts andupon movement of said cam bar in the opposite direction all of saidmovable contacts will move simultaneously in the same direction to openpositions.

2. An electric circuit breaker in accordance with claim 1 wherein eachofsaid cam followers include a roller disposed in an associated one ofsaidcam slots and said cam bar has a plurality of guide grooves thereinelongated in the direction of reciprocation of said cam bar, and whereinsaid circuit breaker also has means including guide grooves and guiderollers disposed in said guide grooves for guiding said cam bar in itsdirection of reciprocation and preventing movement thereof in alldirections transverse to its direction of reciprocation.

3. In an electric circuit breaker having at least three vacuuminterrupters in parallel vertical array, said interrupters each having apair of separable contacts one of which is stationary and the other ofwhich is axially movable into and out of engagement with said stationarycontact;

operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts, said operating means includingcontact loading compression spring means for transmitting contactclosing motion of each of said cam followers to each of said movablecontacts, and means for deflecting each of said contact loadingcompression spring means to a predetermined loading and for providing apositive connection between said associated cam follower and saidassociated movable contact when said cam follower is moved in contactopening direction and each being adjustable to vary said predeterminedloading; an elongated cam bar supported for reciprocal movement in adirection transverse to the direction in which said movable contacts aremovable; a plurality of identical cam slots formed in said cam bar onefor each movable contact, said cam slots being disposed along a commonaxis, said cam slots having identical configurations including a camtrack portion inclined at an oblique angle to the direction of cam barreciprocation, each cam slot also including a cam track portion at eachend of said inclined portion, said cam slots each operatively receivinga cam follower; pivoted bell crank lever having an arm pivotallyconnected to said reciprocable cam bar; preloaded contact opening springmeans engaging an arm of said bell crank lever and further loaded whensaid cam bar is reciprocated in a direction to close said contacts ofsaid plurality of vacuum interrupters; and, latch means adapted toreleasably engage an arm of said bell crank lever for holding said bellcrank lever and said cam bar in a position wherein said contacts of saidplurality of interrupters are closed,

whereby the forces of said plurality of contact loading compressionspring means-and of said contact opening spring means are additive toopen said plurality of vacuum interrupters.

4. An electric circuit breaker in accordance with claim 3 and includinga trip solenoid provided with an armature movable when said solenoid isenergized from a released position wherein said latch means can latchsaid bell cranklever to a trip position wherein said solenoid trips saidlatch means to free said bell crank lever, said armature having aportion accessible from the exterior of said trip solenoid, a pivotedswitch operating handle engaging said accessible portion of saidarmature and being adapted to move said armature from said releasedposition to said trip position, and spring means engaging saidaccessible portion of said armature for normally holding said armaturein said released position and thereby preventing inadvertent opening ofsaid vacuum switch contacts when said operating handle is engaged with ahot stick.

5. In an electric circuit breaker, in combination;

a supporting base;

a plurality of vacuum interrupters mounted in spaced relation on saidbase in a plane transverse to said base and each having a stationarycontact, movable contact, and means including a cam follower foroperating said movable contact into and out of engagement with saidstationary contact;

elongated reciprocable cam bar means having a plurality of cam slotstherein each of which has a cam track portion oblique to the directionof cam reciprocation receiving one of said cam followers forsimultaneously actuating said movable contact operating means of saidplurality of vacuum interrupters;

means affixed to said supporting base for guiding and supporting saidcam bar for reciprocation in said plane transverse to said base;

a mounting plate, said cam bar guiding means supporting said mountingplate in said plane transverse to said base;

bell crank lever means pivoted on said mounting plate and having one armoperatively connected to said reciprocable cam bar;

switch opening spring means affixed at one end to an arm of said bellcrank lever means and at the other end to said mounting plate and beingfurther loaded when said cam bar is reciprocated in the switch closingdirection;

latch means pivotally supported on said mounting plate for latching saidbell crank lever when said cam bar is in switch closing position; and

trip solenoid means affixed to said mounting plate for releasing saidlatch means to free said bell crank lever means when said trip solenoidis energized.

'6. An electric circuit breaker in accordance with claim 5 and includinga closing solenoid supported on said mounting plate and having a plungeroperatively connected to an arm of said bell crank lever means foractuating said cam bar to switch closing position when said closingsolenoid is energized.

7. An electric circuit breaker in accordance with claim 6 wherein saidtrip solenoid is provided with an armature movable when said tripsolenoid is energized from a released position wherein said latch meanscan latch said bell crank lever means to a trip position wherein saidtrip solenoid armature trips said latch means to free said bell cranklever means, said trip solenoid armature having an accessible portion;

a switch operating handle pivotally supported on said mounting plate andbeing adapted to move said trip solenoid armature from said releasedposition to said trip position; and,

spring means engaging said accessible portion of said trip solenoidarmature for normally holding said armature in said released position,thereby preventing inadvertent opening of said vacuum interruptercontacts when said operating handle is engaged with a hot stick.

8. An electric circuit breaker in accordance with claim 5 whereinsaidcam bar guiding and supporting means includes'a plurality of alignedpairs of cam guide legs projecting from the side of said supporting baseopposite that on which said vacuum interrupters are mounted and with thelegs of each said pair being spaced apart and disposed on opposite sidesof a plane transverse to said base and of said cam bar and affixedadjacent their ends to said mounting plate.

9. An electric circuit breaker in accordance with claim 8 wherein saidcam bar has a plurality of cam grooves therein elongated in thedirection of cam bar reciprocation each of which is adjacent one of saidpairs of cam guide legs, and said cam bar guiding and supporting meansincludes said cam grooves, a roller in 1 each of said cam grooves, and aroller support member extending through each said pair of cam guide legsand revolvably supporting one of said rollers with the corresponding camgroove.

10. An electric circuit breaker in accordance with claim 9 wherein eachsaid movable contact operating means includes yoke means pivotallymounted at one end on one of said roller support members and operativelyconnected at the other end to one of said cam followers for guiding saidmovable contact in a manner to insure substantial face-to-faceengagement between contacts when in closed positions.

11. An electric circuit breaker in accordance with claim 10 wherein eachsaid movable contact operating means also includes an elongated,longitudinally reciprocable, insulated contact operating rod operativelyconnected at one end to the associated movable contact and precompressedcontact loading compression spring means for transmitting switch closingcam follower motion to the other end of said contact operating rod.

12. In an electric circuit breaker having at least three interrupters inparallel vertical array, said interrupters each having a pair ofseparable contacts one of which is stationary and the other of which isaxially movable into and out of engagement with said stationary contact;

operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts;

an elongated cam bar supported for reciprocal movement in a directiontransverse to the direction in which said movable contacts are movable;

a plurality of identical cam slots formed in said cam bar one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam track portioninclined at a oblique angle to the direction of cam bar reciprocation,each slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving a camfollower;

an elongated, longitudinally reciprocable, insulated contact operatingrod for each axially movable contact, said operating rods beingoperatively connected to an adjacent end of an associated movablecontact;

precompressed contact loading compression spring means for transmittingswitch closing cam follower motion to the other end of each of saidcontact rods;

a U-shaped stirrup bracketing each of said cam followers and anassociated contact operating rod, each of said U-shaped stirrups havingthe legs thereof operatively coupled to an associated cam follower, saidcontact loading compression spring means being adaptedto react at itsopposite ends against the cross piece of said U-shaped stirrup andagainst said other end of said associated contact operating rod;

adjustable bolt means affixed to said other end of each of said contactoperating rods for precompressing said contact loading compressionspring means against the cross piece of said U-shaped stirrup and forvarying the stroke of said contact operating rod resulting from switchclosing motion of said cam follower; and,

a pivoted member for each of said cam followers operatively connected toan adjacent end of an associated insulated contact operating rod forguiding the movement of the adjacent lower end of an asso ciated movablecontact in an arcuate path of travel that terminates on a line thatincludes the axes of said contacts when said contacts are in closedposition to thereby provide a wiping engagement between the contactfaces of said contacts.

13. In an electric circuit breaker having at'least three vacuuminterrupters in parallel vertical array, said interrupters each having apair of separable contacts one of which is stationary and the other ofwhich is axially movable into and out of engagement with said stationarycontact;

operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into an out of engagement withtheir associated stationary contacts;

an elongated cam bar supported for reciprocal movement in a directiontransverse to the direction in which said movable contacts are movable;

a plurality of identical cam slots formed in said cam bar one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam truck portioninclined at an oblique angle to the direction of cam bar reciprocation,each cam slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving a camfollower;

an elongated, longitudinally reciprocable, insulated contact operatingrod for each axially movable contact, said operating rods beingoperatively connected to an adjacent end of an associated movablecontact;

precompressed contact loading compression spring means for transmittingswitch closing cam follower motion to the other end of each of saidcontact rods;

a U-shaped stirrup bracketing each of said cam followers and said otherend of an associated contact operating rod;

individual bolt means extending through the legs of each of saidstirrups and through said associated cam followerfor coupling saidstirrups to said cam followers, wherein said contact loading compressionspring means react at one end against the cross piece of associatedstirrups and at the opposite end against said other end of an associatedcontact operating rod;

individual bolt means affixed to said other end of each of said contactoperating rods and extending through an associated contact loadingcompression spring means and through a clearance aperture in the crosspiece of an associated stirrup for adjusting the position of saidoperating rod relative to the cross piece of its associated U-shapedstirrup to thereby provide means for varying the preloading of saidcontact loading compression spring means and the stroke of said contactoperating rod as desired; and,

a pivoted member for each of said insulated contact operating rodoperatively connected to an adjacent end of an associated cam followerfor guiding the movement of the adjacent lower end of an associatedmovable contact in an accurate path of travel that terminates on a linethat includes the axes of said contacts when said contacts are in closedposition to thereby provide a wiping engagement between the contactfaces of said contacts.

14. in an electric circuit breaker, in combination;

a supporting base;

a plurality of vacuum interrupters mounted in spaced relation on saidbase in a plane transverse to said base and each having a stationarycontact, a movable contact, and means including a cam follower foroperating said movable contact into and out of engagement with saidstationary contact;

elongated reciprocable cam bar means having a plurality of cam slotstherein each of which has a cam track portion oblique to the directionof cam reciprocation receiving one of said cam followers forsimultaneously actuating said movable contact operating means of saidplurality of vacuum interrupters;

means affixed to said supporting base for guiding and supporting saidcam bar for reciprocation in said plane transverse to said base;

a mounting plate, said cam bar guiding means supporting said mountingplate in said plane transverse to said base;

bell crank lever means pivoted on said mounting plate and having one armoperatively connected to said reciprocable cam bar;

switch opening spring means affixed at one end to an arm of said bellcrank lever means and at the other end to said mounting plate and beingfurther loaded when said cam bar is reciprocated in the switch closingdirection;

latch means pivotally supported on said mounting plate for latching saidbell crank lever when said cam bar is in switch closing position;

trip solenoid means affixed to said mounting plate for releasing saidlatch means to free said bell crank lever means when said trip solenoidis energized, said trip solenoid being provided with an armature movablewhen said trip solenoid is energized from a released position whereinsaid latch means can latch said bell crank lever means to a tripposition wherein said trip solenoid armature trips said latch means tofree said bell crank lever means, said trip solenoid armature having anaccessible portion;

a switch operating handle pivotally supported on said mounting plate andbeing adapted to move said trip solenoid armature from said releasedposition to said trip position, said switch operating handle having alever arm operatively connected to said cam bar, wherein manualoperation of said handle in one direction reciprocates said cam bar toswitch closing position and operation thereof in the opposite directionactuates said trip solenoid armature to said trip position to releasesaid latch means;

spring means engaging said accessible portion of said trip solenoidarmature for normally holding said armature in said released position,thereby preventing inadvertent opening of said vacuum interruptercontacts when said operating handle is engaged with a hot stick; and,

a closing solenoid supported on said mounting plate and having a plungeroperatively connected to an arm of said bell crank lever means foractuating said cam bar to switch closing position when said closingsolenoid is energized.

15. In an electric circuit breaker, in combination;

a supporting base;

a plurality of vacuum interrupters mounted in spaced relation on saidbase in a plane transverse to said base and each having a stationarycontact, a movable contact, and means including a cam follower foroperating said movable contact into and out of engagement with saidstationary contact, each said movable contact operating means includesyoke means pivotally mounted at one end on one of said roller supportmembers and operatively connected at the other end to one of said camfollowers for guiding said movable contact in essentially straight lineaxial motion as it is actuated between open and closed positions, eachsaid movable contact operating means also includes an elongated,longitudinally reciprocable, insulated contact operating rod operativelyconnected at one end to the associated movable contact and precompressedcontact loading compression spring means for transmitting switch closingcam follower motion to the other end of said contact operating rod;

each said movable contact operating means also includes a U-shapedstirrup bracketing said contact loading compression spring means andhaving the legs thereof operatively connected to said cam follower, andwherein said contact loading spring means react at one end against thecross piece of said U-shaped stirrup and at the opposite end againstsaid other end of said contact operating rod;

elongated reciprocable cam bar means having a plurality of cam slotstherein each of which has a cam track portion oblique to the directionof cam reciprocation receiving one of said cam followers forsimultaneously actuating said movable contact operating means of saidplurality of vacuum interrupters;

means affixed to said supporting base for guiding and supporting saidcam for reciprocation in the plane transverse to said base;

said cam bar guiding and supporting means includes a plurality ofaligned pairs of cam guide legs projecting from the side of saidsupporting base opposite that on which said vacuum interrupters aremounted and with the legs of each said pair being spaced apart anddisposed on opposite sides of the plane'transverse to said base and ofsaid cam bar and affixed adajcent their ends to said mounting plate;

said cam bar has a plurality of cam grooves therein elongated in thedirection of cam bar reciprocation each of which is adjacent one of saidpairs of cam guide legs, said cam bar guiding and supporting meansincludes said cam grooves, a roller in each of said cam grooves, and aroller support member extending through each said pair of cam guide legsand revolvably supporting one of said rollers within the correspondingcam groove;

a mountingplate, said cam bar guiding means supporting said mountingplate in the plate transverse to said base;

bell crank lever means pivoted on said mounting plate and having one armoperatively connected to said reciprocable cam bar;

switch opening spring means affixed at one end to an arm of said bellcrank lever means and at the other end to said mounting plate and beingfurther loaded when said cam bar is reciprocated in the switch closingdirection;

latch means pivotally supported on said mounting plate for latching saidbell crank lever when said cam bar is in switch closing position; and,

a trip solenoid affixed to said mounting plate for releasing said latchmeans to free said bell crank lever means when said trip solenoid isenergized.

16. An electric circuit breaker in accordance with claim 15 wherein eachsaid movable contact operating means includes bolt means affixed to saidother end of said contact operating rod and extending through aclearance aperture in said cross piece of said stirrup for adjusting thedeflection of said contact loading spring means and the stroke of saidcontact operating rod resulting from contact closing motion of said camfollower.

l7. An electric circuit breaker in accordance with claim 16 wherein eachsaid cam slot in said cam bar also has cam track portions at each end ofsaid oblique cam track portion extending parallel to the direction ofreciprocation of said cam bar.

18. in an electric circuit breaker having at least three interrupters inparallel vertical array, said interrupters each having a pair ofseparable contacts one of which is stationary and the other of which isaxially movable into and out of engagement with said stationary contact;

operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts, said operating means includescontact loading compression spring means for transmitting contactclosing motion of each of said cam followers to each of movable contact;

means for deflecting each of said contact loading compression springmeans to a predetermined loading and for providing a positive connectionbetween said associated cam follower and said associated movable contactwhen said cam follower is moved in a contact opening direction and eachbeing adjustable to vary said predetermined loadsaid means fordeflecting said contact loading compression spring means is adjustablewhen said pair of contacts are open to vary the predetermined loading ofsaid contact loading compression spring means and thus change the strokethrough which said contact operating means is actuated by said camfollower in a manner that the closing of said pairs of contacts of saidplurality of vacuum interrupters can be synchronized at a single pointin each of said movable contact operating means;

each said movable contact operating means includes an elongated,insulated, axially reciprocable contact operating rod operativelyconnected at one end to said movable contact, a U-shaped stirrupembracing said contact loading compression spring means and the otherend of said operating rod and said cam follower and having the legs ofsaid U- shaped stirrup coupled to said cam follower, and wherein saidcontact loading compression spring means reacts at one end against thecross piece of said U-shaped stirrup and at its opposite end againstsaid other end of said operating rod;

an elongated cam bar supported for reciprocable movement in a directiontransverse to the direction in which said movable contacts are movable;and,

a plurality of identical cam slots formed in said cam bar one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam track portioninclined at an oblique angle to the direction of cam bar reciprocation,each cam slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving a camfollower.

19. An electric circuit breaker in accordance with claim 18 andincluding bolt means affixed at one end to said contact operating rodand extending through said contact loading compression spring means andalso through a clearance hole in said cross piece of said U-shapedstirrup for deflecting said contact loading springs to a predeterminedloading and for providing a positive connection between said camfollower and said contact operating rod when said cam follower isactuated in a contact opening direction and permitting relative movementtherebetween when said cam follower is actuated in a contact closingdirection, said bolt means being adjustable to vary the deflection ofsaid contact loading springs and the contact closing stroke of saidcontact operating rod.

20. An electric circuit breaker in accordance with claim 19 wherein eachsaid movable contact operating means includes pivoted yoke meansoperatively connected to said cam follower for guiding said other end ofsaid contact operating rod in substantially straight line motion axiallyof said movable contact as said cam follower is actuated by said cambar.

1. In an electric circuit breaker having at least three interrupters inparallel vertical array, said interrupters each having a pair ofseparable contacts one of which is stationary and the other of which isaxially movable into and out of engagement with said stationary contact;opErating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts; an elongated cam bar supported forreciprocal movement in a direction transverse to the direction in whichsaid movable contacts are movable; a plurality of identical cam slotsformed in said cam bar, one for each movable contact, said cam slotsbeing disposed along a common axis, said cam slots having identicalconfigurations including a cam track portion inclined at an obliqueangle to the direction of cam bar reciprocation, each cam slot alsoincluding a cam track portion at each end of said inclined portion, saidcam slots each operatively receiving a cam follower; a pivoted yoke foreach cam follower and operatively connected to each cam follower forguiding the lower end of said contact in such a manner that in theclosing movement said movable contacts move in an arcuate path of travelthat terminates on a line that includes the axes of the contacts whensaid contacts are in closed position to thereby provide a wipingengagement between the contact faces of said contacts; and, a contactloading compression spring for each of said contacts, said loadingcompression spring being supported in position to provide forpredetermined high pressure engagement between the movable contact andan associated stationary contact irrespective of the amount of overtravel of an associated cam follower, whereby movement of said cam barin one direction will effect simultaneous movement of all of saidmovable contacts in the same direction into engagement with theirassociated stationary contacts and upon movement of said cam bar in theopposite direction all of said movable contacts will move simultaneouslyin the same direction to open positions.
 2. An electric circuit breakerin accordance with claim 1 wherein each of said cam followers include aroller disposed in an associated one of said cam slots and said cam barhas a plurality of guide grooves therein elongated in the direction ofreciprocation of said cam bar, and wherein said circuit breaker also hasmeans including guide grooves and guide rollers disposed in said guidegrooves for guiding said cam bar in its direction of reciprocation andpreventing movement thereof in all directions transverse to itsdirection of reciprocation.
 3. In an electric circuit breaker having atleast three vacuum interrupters in parallel vertical array, saidinterrupters each having a pair of separable contacts one of which isstationary and the other of which is axially movable into and out ofengagement with said stationary contact; operating means including a camfollower operably connected to each of said axially movable contacts foractuating all of said contacts simultaneously in the same direction intoand out of engagement with their associated stationary contacts, saidoperating means including contact loading compression spring means fortransmitting contact closing motion of each of said cam followers toeach of said movable contacts, and means for deflecting each of saidcontact loading compression spring means to a predetermined loading andfor providing a positive connection between said associated cam followerand said associated movable contact when said cam follower is moved incontact opening direction and each being adjustable to vary saidpredetermined loading; an elongated cam bar supported for reciprocalmovement in a direction transverse to the direction in which saidmovable contacts are movable; a plurality of identical cam slots formedin said cam bar one for each movable contact, said cam slots beingdisposed along a common axis, said cam slots having identicalconfigurations including a cam track portion inclined at an obliqueangle to the direction of cam bar reciprocation, each cam slot alsoincluding a cam track portion At each end of said inclined portion, saidcam slots each operatively receiving a cam follower; a pivoted bellcrank lever having an arm pivotally connected to said reciprocable cambar; preloaded contact opening spring means engaging an arm of said bellcrank lever and further loaded when said cam bar is reciprocated in adirection to close said contacts of said plurality of vacuuminterrupters; and, latch means adapted to releasably engage an arm ofsaid bell crank lever for holding said bell crank lever and said cam barin a position wherein said contacts of said plurality of interruptersare closed, whereby the forces of said plurality of contact loadingcompression spring means and of said contact opening spring means areadditive to open said plurality of vacuum interrupters.
 4. An electriccircuit breaker in accordance with claim 3 and including a trip solenoidprovided with an armature movable when said solenoid is energized from areleased position wherein said latch means can latch said bell cranklever to a trip position wherein said solenoid trips said latch means tofree said bell crank lever, said armature having a portion accessiblefrom the exterior of said trip solenoid, a pivoted switch operatinghandle engaging said accessible portion of said armature and beingadapted to move said armature from said released position to said tripposition, and spring means engaging said accessible portion of saidarmature for normally holding said armature in said released positionand thereby preventing inadvertent opening of said vacuum switchcontacts when said operating handle is engaged with a hot stick.
 5. Inan electric circuit breaker, in combination; a supporting base; aplurality of vacuum interrupters mounted in spaced relation on said basein a plane transverse to said base and each having a stationary contact,movable contact, and means including a cam follower for operating saidmovable contact into and out of engagement with said stationary contact;elongated reciprocable cam bar means having a plurality of cam slotstherein each of which has a cam track portion oblique to the directionof cam reciprocation receiving one of said cam followers forsimultaneously actuating said movable contact operating means of saidplurality of vacuum interrupters; means affixed to said supporting basefor guiding and supporting said cam bar for reciprocation in said planetransverse to said base; a mounting plate, said cam bar guiding meanssupporting said mounting plate in said plane transverse to said base;bell crank lever means pivoted on said mounting plate and having one armoperatively connected to said reciprocable cam bar; switch openingspring means affixed at one end to an arm of said bell crank lever meansand at the other end to said mounting plate and being further loadedwhen said cam bar is reciprocated in the switch closing direction; latchmeans pivotally supported on said mounting plate for latching said bellcrank lever when said cam bar is in switch closing position; and tripsolenoid means affixed to said mounting plate for releasing said latchmeans to free said bell crank lever means when said trip solenoid isenergized.
 6. An electric circuit breaker in accordance with claim 5 andincluding a closing solenoid supported on said mounting plate and havinga plunger operatively connected to an arm of said bell crank lever meansfor actuating said cam bar to switch closing position when said closingsolenoid is energized.
 7. An electric circuit breaker in accordance withclaim 6 wherein said trip solenoid is provided with an armature movablewhen said trip solenoid is energized from a released position whereinsaid latch means can latch said bell crank lever means to a tripposition wherein said trip solenoid armature trips said latch means tofree said bell crank lever means, said trip solenoid armature having anaccessible portion; a switch operating handle pivotally supported onsaId mounting plate and being adapted to move said trip solenoidarmature from said released position to said trip position; and, springmeans engaging said accessible portion of said trip solenoid armaturefor normally holding said armature in said released position, therebypreventing inadvertent opening of said vacuum interrupter contacts whensaid operating handle is engaged with a hot stick.
 8. An electriccircuit breaker in accordance with claim 5 wherein said cam bar guidingand supporting means includes a plurality of aligned pairs of cam guidelegs projecting from the side of said supporting base opposite that onwhich said vacuum interrupters are mounted and with the legs of eachsaid pair being spaced apart and disposed on opposite sides of a planetransverse to said base and of said cam bar and affixed adjacent theirends to said mounting plate.
 9. An electric circuit breaker inaccordance with claim 8 wherein said cam bar has a plurality of camgrooves therein elongated in the direction of cam bar reciprocation eachof which is adjacent one of said pairs of cam guide legs, and said cambar guiding and supporting means includes said cam grooves, a roller ineach of said cam grooves, and a roller support member extending througheach said pair of cam guide legs and revolvably supporting one of saidrollers with the corresponding cam groove.
 10. An electric circuitbreaker in accordance with claim 9 wherein each said movable contactoperating means includes yoke means pivotally mounted at one end on oneof said roller support members and operatively connected at the otherend to one of said cam followers for guiding said movable contact in amanner to insure substantial face-to-face engagement between contactswhen in closed positions.
 11. An electric circuit breaker in accordancewith claim 10 wherein each said movable contact operating means alsoincludes an elongated, longitudinally reciprocable, insulated contactoperating rod operatively connected at one end to the associated movablecontact and precompressed contact loading compression spring means fortransmitting switch closing cam follower motion to the other end of saidcontact operating rod.
 12. In an electric circuit breaker having atleast three interrupters in parallel vertical array, said interrupterseach having a pair of separable contacts one of which is stationary andthe other of which is axially movable into and out of engagement withsaid stationary contact; operating means including a cam followeroperably connected to each of said axially movable contacts foractuating all of said contacts simultaneously in the same direction intoand out of engagement with their associated stationary contacts; anelongated cam bar supported for reciprocal movement in a directiontransverse to the direction in which said movable contacts are movable;a plurality of identical cam slots formed in said cam bar one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam track portioninclined at a oblique angle to the direction of cam bar reciprocation,each slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving a camfollower; an elongated, longitudinally reciprocable, insulated contactoperating rod for each axially movable contact, said operating rodsbeing operatively connected to an adjacent end of an associated movablecontact; precompressed contact loading compression spring means fortransmitting switch closing cam follower motion to the other end of eachof said contact rods; a U-shaped stirrup bracketing each of said camfollowers and an associated contact operating rod, each of said U-shapedstirrups having the legs thereof operatively coupled to an associatedcam follower, said contact loading compression spring means beingadapted to react at its opposite ends against the cross piece of saidU-shaped stirrup and against said other end of said associated contactoperating rod; adjustable bolt means affixed to said other end of eachof said contact operating rods for precompressing said contact loadingcompression spring means against the cross piece of said U-shapedstirrup and for varying the stroke of said contact operating rodresulting from switch closing motion of said cam follower; and, apivoted member for each of said cam followers operatively connected toan adjacent end of an associated insulated contact operating rod forguiding the movement of the adjacent lower end of an associated movablecontact in an arcuate path of travel that terminates on a line thatincludes the axes of said contacts when said contacts are in closedposition to thereby provide a wiping engagement between the contactfaces of said contacts.
 13. In an electric circuit breaker having atleast three vacuum interrupters in parallel vertical array, saidinterrupters each having a pair of separable contacts one of which isstationary and the other of which is axially movable into and out ofengagement with said stationary contact; operating means including a camfollower operably connected to each of said axially movable contacts foractuating all of said contacts simultaneously in the same direction intoan out of engagement with their associated stationary contacts; anelongated cam bar supported for reciprocal movement in a directiontransverse to the direction in which said movable contacts are movable;a plurality of identical cam slots formed in said cam bar one for eachmovable contact, said cam slots being disposed along a common axis, saidcam slots having identical configurations including a cam truck portioninclined at an oblique angle to the direction of cam bar reciprocation,each cam slot also including a cam track portion at each end of saidinclined portion, said cam slots each operatively receiving a camfollower; an elongated, longitudinally reciprocable, insulated contactoperating rod for each axially movable contact, said operating rodsbeing operatively connected to an adjacent end of an associated movablecontact; precompressed contact loading compression spring means fortransmitting switch closing cam follower motion to the other end of eachof said contact rods; a U-shaped stirrup bracketing each of said camfollowers and said other end of an associated contact operating rod;individual bolt means extending through the legs of each of saidstirrups and through said associated cam follower for coupling saidstirrups to said cam followers, wherein said contact loading compressionspring means react at one end against the cross piece of associatedstirrups and at the opposite end against said other end of an associatedcontact operating rod; individual bolt means affixed to said other endof each of said contact operating rods and extending through anassociated contact loading compression spring means and through aclearance aperture in the cross piece of an associated stirrup foradjusting the position of said operating rod relative to the cross pieceof its associated U-shaped stirrup to thereby provide means for varyingthe preloading of said contact loading compression spring means and thestroke of said contact operating rod as desired; and, a pivoted memberfor each of said insulated contact operating rod operatively connectedto an adjacent end of an associated cam follower for guiding themovement of the adjacent lower end of an associated movable contact inan accurate path of travel that terminates on a line that includes theaxes of said contacts when said contacts are in closed position tothereby provide a wiping engagement between the contact faces of saidcontacts.
 14. In an electric circuit breaker, in combination; asupporting base; a plurality of vacuum interrupters mounted in spacedrelation on said base in a plane transverse to said base and each havinga stationary contact, a mOvable contact, and means including a camfollower for operating said movable contact into and out of engagementwith said stationary contact; elongated reciprocable cam bar meanshaving a plurality of cam slots therein each of which has a cam trackportion oblique to the direction of cam reciprocation receiving one ofsaid cam followers for simultaneously actuating said movable contactoperating means of said plurality of vacuum interrupters; means affixedto said supporting base for guiding and supporting said cam bar forreciprocation in said plane transverse to said base; a mounting plate,said cam bar guiding means supporting said mounting plate in said planetransverse to said base; bell crank lever means pivoted on said mountingplate and having one arm operatively connected to said reciprocable cambar; switch opening spring means affixed at one end to an arm of saidbell crank lever means and at the other end to said mounting plate andbeing further loaded when said cam bar is reciprocated in the switchclosing direction; latch means pivotally supported on said mountingplate for latching said bell crank lever when said cam bar is in switchclosing position; trip solenoid means affixed to said mounting plate forreleasing said latch means to free said bell crank lever means when saidtrip solenoid is energized, said trip solenoid being provided with anarmature movable when said trip solenoid is energized from a releasedposition wherein said latch means can latch said bell crank lever meansto a trip position wherein said trip solenoid armature trips said latchmeans to free said bell crank lever means, said trip solenoid armaturehaving an accessible portion; a switch operating handle pivotallysupported on said mounting plate and being adapted to move said tripsolenoid armature from said released position to said trip position,said switch operating handle having a lever arm operatively connected tosaid cam bar, wherein manual operation of said handle in one directionreciprocates said cam bar to switch closing position and operationthereof in the opposite direction actuates said trip solenoid armatureto said trip position to release said latch means; spring means engagingsaid accessible portion of said trip solenoid armature for normallyholding said armature in said released position, thereby preventinginadvertent opening of said vacuum interrupter contacts when saidoperating handle is engaged with a hot stick; and, a closing solenoidsupported on said mounting plate and having a plunger operativelyconnected to an arm of said bell crank lever means for actuating saidcam bar to switch closing position when said closing solenoid isenergized.
 15. In an electric circuit breaker, in combination; asupporting base; a plurality of vacuum interrupters mounted in spacedrelation on said base in a plane transverse to said base and each havinga stationary contact, a movable contact, and means including a camfollower for operating said movable contact into and out of engagementwith said stationary contact, each said movable contact operating meansincludes yoke means pivotally mounted at one end on one of said rollersupport members and operatively connected at the other end to one ofsaid cam followers for guiding said movable contact in essentiallystraight line axial motion as it is actuated between open and closedpositions, each said movable contact operating means also includes anelongated, longitudinally reciprocable, insulated contact operating rodoperatively connected at one end to the associated movable contact andprecompressed contact loading compression spring means for transmittingswitch closing cam follower motion to the other end of said contactoperating rod; each said movable contact operating means also includes aU-shaped stirrup bracketing said contact loading compression springmeans and having the legs thereof operatively connected to said camfollower, and wherein Said contact loading spring means react at one endagainst the cross piece of said U-shaped stirrup and at the opposite endagainst said other end of said contact operating rod; elongatedreciprocable cam bar means having a plurality of cam slots therein eachof which has a cam track portion oblique to the direction of camreciprocation receiving one of said cam followers for simultaneouslyactuating said movable contact operating means of said plurality ofvacuum interrupters; means affixed to said supporting base for guidingand supporting said cam for reciprocation in the plane transverse tosaid base; said cam bar guiding and supporting means includes aplurality of aligned pairs of cam guide legs projecting from the side ofsaid supporting base opposite that on which said vacuum interrupters aremounted and with the legs of each said pair being spaced apart anddisposed on opposite sides of the plane transverse to said base and ofsaid cam bar and affixed adajcent their ends to said mounting plate;said cam bar has a plurality of cam grooves therein elongated in thedirection of cam bar reciprocation each of which is adjacent one of saidpairs of cam guide legs, said cam bar guiding and supporting meansincludes said cam grooves, a roller in each of said cam grooves, and aroller support member extending through each said pair of cam guide legsand revolvably supporting one of said rollers within the correspondingcam groove; a mounting plate, said cam bar guiding means supporting saidmounting plate in the plate transverse to said base; bell crank levermeans pivoted on said mounting plate and having one arm operativelyconnected to said reciprocable cam bar; switch opening spring meansaffixed at one end to an arm of said bell crank lever means and at theother end to said mounting plate and being further loaded when said cambar is reciprocated in the switch closing direction; latch meanspivotally supported on said mounting plate for latching said bell cranklever when said cam bar is in switch closing position; and, a tripsolenoid affixed to said mounting plate for releasing said latch meansto free said bell crank lever means when said trip solenoid isenergized.
 16. An electric circuit breaker in accordance with claim 15wherein each said movable contact operating means includes bolt meansaffixed to said other end of said contact operating rod and extendingthrough a clearance aperture in said cross piece of said stirrup foradjusting the deflection of said contact loading spring means and thestroke of said contact operating rod resulting from contact closingmotion of said cam follower.
 17. An electric circuit breaker inaccordance with claim 16 wherein each said cam slot in said cam bar alsohas cam track portions at each end of said oblique cam track portionextending parallel to the direction of reciprocation of said cam bar.18. In an electric circuit breaker having at least three interrupters inparallel vertical array, said interrupters each having a pair ofseparable contacts one of which is stationary and the other of which isaxially movable into and out of engagement with said stationary contact;operating means including a cam follower operably connected to each ofsaid axially movable contacts for actuating all of said contactssimultaneously in the same direction into and out of engagement withtheir associated stationary contacts, said operating means includescontact loading compression spring means for transmitting contactclosing motion of each of said cam followers to each of movable contact;means for deflecting each of said contact loading compression springmeans to a predetermined loading and for providing a positive connectionbetween said associated cam follower and said associated movable contactwhen said cam follower is moved in a contact opening direction and eachbeing adjustable to vary said predetermined loading; said means fordeflecting said contact loading compression spring means is adjustablewhen said pair of contacts are open to vary the predetermined loading ofsaid contact loading compression spring means and thus change the strokethrough which said contact operating means is actuated by said camfollower in a manner that the closing of said pairs of contacts of saidplurality of vacuum interrupters can be synchronized at a single pointin each of said movable contact operating means; each said movablecontact operating means includes an elongated, insulated, axiallyreciprocable contact operating rod operatively connected at one end tosaid movable contact, a U-shaped stirrup embracing said contact loadingcompression spring means and the other end of said operating rod andsaid cam follower and having the legs of said U-shaped stirrup coupledto said cam follower, and wherein said contact loading compressionspring means reacts at one end against the cross piece of said U-shapedstirrup and at its opposite end against said other end of said operatingrod; an elongated cam bar supported for reciprocable movement in adirection transverse to the direction in which said movable contacts aremovable; and, a plurality of identical cam slots formed in said cam barone for each movable contact, said cam slots being disposed along acommon axis, said cam slots having identical configurations including acam track portion inclined at an oblique angle to the direction of cambar reciprocation, each cam slot also including a cam track portion ateach end of said inclined portion, said cam slots each operativelyreceiving a cam follower.
 19. An electric circuit breaker in accordancewith claim 18 and including bolt means affixed at one end to saidcontact operating rod and extending through said contact loadingcompression spring means and also through a clearance hole in said crosspiece of said U-shaped stirrup for deflecting said contact loadingsprings to a predetermined loading and for providing a positiveconnection between said cam follower and said contact operating rod whensaid cam follower is actuated in a contact opening direction andpermitting relative movement therebetween when said cam follower isactuated in a contact closing direction, said bolt means beingadjustable to vary the deflection of said contact loading springs andthe contact closing stroke of said contact operating rod.
 20. Anelectric circuit breaker in accordance with claim 19 wherein each saidmovable contact operating means includes pivoted yoke means operativelyconnected to said cam follower for guiding said other end of saidcontact operating rod in substantially straight line motion axially ofsaid movable contact as said cam follower is actuated by said cam bar.